Hi Jakub,
There is a chunck of code in Evince that inspect PDF metadata, however, I think it should be removed sooner or later because
1) The tags used by Creative Commons licenses are not well stablished and/or used. It is something it must be revisited.
2) As José and German said, possibly poppler is a better place for this piece of code.
Cheers,
-- Juanjo Marin
